Generally, a secondary battery is designed to be recharged dissimilar to a non-rechargeable primary battery, and has a wide range of applications, for example, electronic devices including mobile phones, lap-top computers and camcorders, electric vehicles, and the like. In particular, a lithium secondary battery has an operating voltage of about 3.6V and a capacity about three times higher than a Ni—Cd battery or Ni-MH battery which is widely used as a power source of electronic equipments, as well as a high energy density per unit weight, and thus its extent of utilization is showing a fast growing tendency.
Such a lithium secondary battery mainly uses lithium-based oxide and a carbon material as a cathode active material and an anode active material, respectively. A lithium secondary battery includes an electrode assembly consisting of a cathode plate coated with the cathode active material, an anode plate coated with the anode active material, and a separator interposed therebetween, and an outer casing to sealingly receive the electrode assembly therein along with an electrolyte solution.
Meanwhile, a lithium secondary battery may be classified, based on a shape of a battery casing, into a can-shaped secondary battery in which an electrode assembly is embedded in a metal casing and a pouch-shaped secondary battery in which an electrode assembly is embedded in a pouch of an aluminum laminate sheet.
A secondary battery is generally manufactured by injecting an electrolyte in a liquid state, that is, an electrolyte solution, in such a state that an electrode assembly is received in a battery casing, and by sealing the battery casing.
FIG. 1 is a cross sectional view of a conventional pouch-shaped secondary battery when viewed from the front, and FIG. 2 is a cross sectional view of section A of FIG. 1 when viewed from the side.
Referring to FIGS. 1 and 2, generally, a secondary battery has such a configuration that an electrode assembly 10 and an electrolyte solution are received in an internal space of a battery casing 20. The electrode assembly 10 includes a cathode plate and an anode plate with a separator interposed therebetween, and each of the cathode plate and the anode plate has an electrode tab 11 attached thereto. Also, the electrode tabs 11 are received in the internal space of the electrode casing 20 indicated by section V in the drawing in such a state that the electrode tabs 11 are connected to electrode leads 12. However, conventionally, connections of the electrode tabs 11 and the electrode leads 12 are made in a curved state in a shape of a letter V, as shown in FIG. 2, to reduce a space occupied thereby. For this reason, a space occupied by connected portions of the electrode tabs 11 and the electrode leads 12 in the battery casing 20 are referred to as a V-forming space.
However, the electrode assembly 10 may be moveable due to the presence of an empty space inside the battery casing 20 such as a V-forming space. When the electrode assembly 10 moves, the electrode tabs 11, the electrode leads 12, and their connected portions may be damaged, and moreover, the electrode assembly 10 itself may be damaged.
Further, when the electrode tabs 11 are cut off due to the movement of the electrode assembly 10, the cut-off portion may come into contact with an electrode plate of opposite polarity to cause an internal short circuit, which in this case, may lead to a grave issue, for example, an accident such as heat generation, a fire, or explosion of the secondary battery.